1. Field of the Invention
This invention generally relates to electromagnetically actuated switches and more specifically to a method and apparatus for verifying correct positions of a contact in a switch.
2. Description of the Prior Art
Commercially well known reed relay usually includes two flat reed contacts enclosed in a sealed tube. The reed contacts are made from soft magnetic material and serve as a core for transferring magnetic flux. When a magnetic field is produced by energizing a winding that surrounds the tube, the reed contacts are mutually magnetically attracted into a contact engagement. To achieve consistent contact resistance, the reed contacts must be perfectly parallel and precisely positioned. Incorrect contact position, due to manufacturing imperfections or misuse, may adversely affect performance and life span of the relay. A certain degree of operational integrity of a relay may be verified by measuring resistance of its contacts when the relay is energized. However, such tests do not reveal slightly misaligned contacts, do not unveil marginal relays, and it is not always practical to perform them in complex devices that contain large numbers of relays.
A switching device in the form of a reed relay including a pair of magnetically soft reed contacts and control winding for effecting closure of the contacts is disclosed in U.S. Pat. No. 3,070,677 issued on Dec. 25, 1962 to Terrell N. Lowry.
A switching device capable of displaying different positions of its contact by respectively different colors is unknown.
A multicolor semiconductor lamp comprising a plurality of light emitting diodes for emitting light of respectively different colors is disclosed in U.S. Pat. No. 3,875,456 issued on Apr. 1, 1975 to Tsuyoshi Kano et al. The light emitting diodes are closely adjacent and covered by a layer of light scattering material to provide an appearance of a single light source.